To measure the effect of a physical activity intervention, based on social cognitive theory, delivered by a peer and a professional leader. Quasi-experimental. Three locations at a large Mid-Western railroad. One hundred and forty-eight skilled labor employees participated: one hundred and twenty completed the study. Self-reported energy expenditure, self-efficacy and stages of change. ANOVA and categorical analysis using rates and proportions were used for evaluation. The peer group had a non-significant short-term increase in energy expenditure of 3%, which returned to baseline post intervention. The professional and control groups showed a non-significant decrease in energy expenditure of 5% and 9%, respectively. The peer (p < 0.002) and professional groups (p < 0.004) showed significant increases in average stages scores. The peer group maintained increases over time (p < 0.001). The peer and professional led groups showed a 54% and 24% increase in the number of employees reporting regular physical activity over time, respectively. The peer group also showed positive trends in self-efficacy. The peer intervention enhanced self-efficacy and self-reported physical activity. A job layoff at the professional led site confounded comparisons between locations. Employees reported high energy expenditure and high BMI values, suggesting that a weight management intervention may be more appropriate and appealing in this population.